Young adults (18-24 years) are particularly prone to unhealthy changes in body composition (average weight gain 30 pounds) that predispose them to development of obesity-related diseases. The proposed research is designed to test the novel hypothesis that active participation in whole-body vibration (WBV) training will result in suppression of accumulation of fat, maintenance of lean muscle mass and reduced levels of risk factors as- sociated with obesity. WBV involves a unique method of stimulating the musculoskeletal system through pas- sive application of high frequency, low amplitude mechanical signals. Based upon our preliminary data and published findings, it is hypothesized that, at the end of 6-months, young adults receiving a 20-minute of WBV 3 d/wk, will not experience weight gain but will instead maintain lean muscle mass compared to those assigned to the control group. This hypothesis is based on our strong preliminary studies, in which we have shown that repeated exposure to WBV reduced age-related increases in fat mass in mature rats while maintaining lean muscle mass. Additional preliminary findings in older adults suggest a WBV intervention to be effective in re- ducing body mass, fat mass and percent body fat while maintaining lean mass. In the proposed study, a 6- month randomized controlled trial will be carried out with two groups: 1) WBV and 2) attention control relaxa- tion group, to test th hypothesis by through the following Aim: To evaluate the therapeutic benefits and feasi- bility of implementing a whole-body vibration (WBV) exercise training program as a method of preventing weight gain and increases in fat mass in physically inactive young adults (18-24 yrs.). Primary outcome meas- ures include: Total body weight, % body fat, fat mass, visceral adipose tissue, and fat free mass, measured by dual energy X-ray absorptiometry (DXA). The proposed study is potentially innovative because it capitalizes on a new therapeutic technique - WBV to improve body composition by stimulating the musculoskeletal system through the passive application of high frequency, low amplitude mechanical signals. Successful completion of the proposed research would establish WBV training as a safe and feasible program with high compliance and acceptability for preventing weight gain in young adults. At the end of 6-months, young adults receiving a 20- min. of WBV 3d/wk will have maintained their body weight and will have a healthier body composition (lean-fat mass). This application addresses the NIH strategic goal to encourage exploratory/developmental clinical re- search that will accelerate development of effective interventions for prevention or treatment of overweight and/or obesity in adults and/or children and, PA-09-124 Exploratory/Developmental Clinical Research Grants in Obesity (R21). This new and substantively different approach is expected to overcome difficulties of recruiting, retaining, and motivating young adults to remain weight stable, often associated with other long term weight programs, thereby resulting in an efficacious approach to weight gain prevention. !